Port Phillip Baykeeper » Wild Things

Cart-rut shells alive and well in Brighton

BayKeeper — Fri, 11 Nov 2011 23:32:25 +0000

A Baykeeper shoreline shell survey found a large Cart-rut shell (Thais orbita) at Holloway Bend earlier this year, suggesting the species may still live in the area. This species was central to the ban on use of Tributyltin (TBT) as an anti-foulant on vessels less that 25m in Victoria in 1989.

Cart-rut shell: worse for wear but there!

International studies had shown TBT caused female shellfish to grow penises. A high incidence of the condition (known as imposex) had been recorded at Brighton Harbour in the early 1990s, but had reduced after the ban. We were delighted this week to receive photos of several “fist-sized” Cart-rut Shells on a reef offshore of Brighton.

Cart-rut shells on Brighton reef (pic: Steven Putt)

10 years after the ban was introduced, Marine Pollution Bulletin (Volume 42 # 10) reported that the relative penis size index (RPSI) of female Thais orbita in Port Phillip Bay had generally reduced. But the RPSI had increased at Williamstown, indicating that TBT from large vessels, ship maintenance activities, and release from historically contaminated sediments, continued to pollute the area.

The study concluded that while the ban remained, TBT pollution would only threaten ports areas and be unlikely to impact more widely in the Bay. Unfortunately, their study was restricted to a limited number of sites and they didn’t consider the practice of dumping dredged sediments from the Port of Melbourne into the Bay.

Thresher shark on Hampton beach

BayKeeper — Tue, 25 Oct 2011 11:49:02 +0000

Beachcombers at Hampton scored a rare treat last week with a dead Thresher Shark (Alopias vulpinus) washed up in the shallows.

Sad end for a stunning shark

Thresher Sharks are widespread around the world but are known live mostly in oceans rather than bays and inlets. It’s quite likely this one has followed the schools of snapper that have come into the bay in the past few weeks.

Their name relates to the long tail (almost as long as the body) which they use to stun fish before swallowing.

Without an autopsy (as it has no visible injuries) any suggestions as to why it died would be pure speculation. But they are known to fall victim to the long-line tuna fishing industry. Perhaps it swallowed a hook some time back which has eventually caused death.

Stray sea lion lobs in Brighton

BayKeeper — Fri, 30 Sep 2011 12:16:25 +0000

You don’t expect to see a sea lion in Port Phillip Bay these days, let alone crossing Beach Road in Brighton. But this curious critter turned up in a Brighton back yard in mid September!

Anybody home???

Reports from early European explorers and bones found in aboriginal middens indicate sea lions once lived in Bass Strait. But their range was probably reduced in the 1800s by the sealing industry. Nowadays their breeding range is believed to be west of Kangaroo Island South Oz; and they are believed to remain close to their birthplace. So the story here is quite a mystery.

Sea lions are closely related to Australian fur seals in that they have ears and larger forelimbs than other seal species; and their hind limbs are capable of a shuffling walk on land.

ahhh well... back to the Bay